Protective Effects of Lipoxin A4 and B4 Signaling on the Inner Retina in a Mouse Model of Experimental Glaucoma.

Glaucoma is a common neurodegenerative disease characterized by progressive degeneration of retinal ganglion cells (RGCs) and the retinal nerve fiber layer (RNFL), resulting in a gradual decline of vision. A recent study by our groups indicated that the levels of lipoxins A4 (LXA4) and B4 (LXB4) in the retina and optic nerve decrease following acute injury, and that restoring their function is neuroprotective. Lipoxins are members of the specialized pro-resolving mediator (SPM) family and play key roles to mitigate and resolve chronic inflammation and tissue damage. Yet, knowledge about lipoxin neuroprotective activity remains limited. Here we investigate the in vivo efficacy of exogenous LXA4 and LXB4 administration on the inner retina in a mouse model of chronic experimental glaucoma. To investigate the contribution of LXA4 signaling we used transgenic knockout (KO) mice lacking the two mouse LXA4 receptors (Fpr2/Fpr3-/-). Functional and structural changes of inner retinal neurons were assessed longitudinally using electroretinogram (ERG) and optical coherence tomography (OCT). At the end of the experiment, retinal samples were harvested for immunohistological assessment. While both lipoxins generated protective trends, only LXB4 treatment was significant, and consistently more efficacious than LXA4 in all endpoints. Both lipoxins also appeared to dramatically reduce Müller glial reactivity following injury. In comparison, Fpr2/Fpr3 deletion significantly worsened inner retinal injury and function, consistent with an essential protective role for endogenous LXA4. Together, these results support further exploration of lipoxin signaling as a treatment for glaucomatous neurodegeneration.

Comparison of laser and circumlimbal suture induced elevation of intraocular pressure in albino CD-1 mice.

Animal models of ocular hypertension are important tools for glaucoma studies. Both acute transient models and chronic models of ocular hypertension may be useful to investigate specific aspects of neurodegeneration. In this study, we compare the intraocular pressure (IOP) and inner retinal changes induced by 1) laser photocoagulation of both episcleral veins and limbal vessels and 2) circumlimbal suture in CD-1 mice. The suture group is divided into 3 subgroups depending on the level of the immediate IOP spike (acute > 55 mmHg or chronic < 55 mmHg) and time period of monitoring (7 or 28 days). The laser group is followed for 7 days. IOP data show that it peaks at 5 hours and returns to normal level within 7 days in the laser group. In all suture groups, IOP spikes initially and decreases gradually, but it remains significantly elevated at 7 days. In 7 days, the acute suture model generates rapid loss of retinal nerve fiber layer (RNFL) and retinal ganglion cells (RGCs) when compared to the gradual loss by the chronic suture model, possibly due to retinal ischemia and reperfusion within the first few hours after treatment. The laser model falls between the acute suture and chronic suture models resulting in less RNFL and RGC loss than the acute suture model but significantly more loss than the chronic suture model. These results suggest that when using suture models of IOP elevation, it is critical to take the initial IOP spike into consideration and to choose between the acute and chronic models depending on respective research purposes.

Astrocyte-derived lipoxins A4 and B4 promote neuroprotection from acute and chronic injury.

Astrocytes perform critical non-cell autonomous roles following CNS injury that involve either neurotoxic or neuroprotective effects. Yet the nature of potential prosurvival cues has remained unclear. In the current study, we utilized the close interaction between astrocytes and retinal ganglion cells (RGCs) in the eye to characterize a secreted neuroprotective signal present in retinal astrocyte conditioned medium (ACM). Rather than a conventional peptide neurotrophic factor, we identified a prominent lipid component of the neuroprotective signal through metabolomics screening. The lipoxins LXA4 and LXB4 are small lipid mediators that act locally to dampen inflammation, but they have not been linked directly to neuronal actions. Here, we determined that LXA4 and LXB4 are synthesized in the inner retina, but their levels are reduced following injury. Injection of either lipoxin was sufficient for neuroprotection following acute injury, while inhibition of key lipoxin pathway components exacerbated injury-induced damage. Although LXA4 signaling has been extensively investigated, LXB4, the less studied lipoxin, emerged to be more potent in protection. Moreover, LXB4 neuroprotection was different from that of established LXA4 signaling, and therapeutic LXB4 treatment was efficacious in a chronic model of the common neurodegenerative disease glaucoma. Together, these results identify a potential paracrine mechanism that coordinates neuronal homeostasis and inflammation in the CNS.

Establishment and Characterization of an Acute Model of Ocular Hypertension by Laser-Induced Occlusion of Episcleral Veins.

Purpose: This study was designed to develop and characterize a laser-induced model of acute intraocular hypertension that permits the study of the anterior segment of the eye. Methods: CD1 mice aged 5 and 8 weeks were examined for elevation of IOP induced by laser photocoagulation. We compared between occlusion of episcleral veins alone and when combined with 270° limbal vessel occlusion. Anterior chamber angle, corneal thickness, and retinal nerve fiber layer (RNFL) thickness were evaluated by anterior- and posterior-segment optical coherence tomography (OCT). Additionally, at day 7 post-procedure, the anterior segment was evaluated for inflammatory cellular presentation by histologic analysis and OCT, and limbal vessels and whole-mount retina were immunostained for CD31 and Brn3a, respectively. Brn3a-positive retinal ganglion cells (RGCs) were quantified with ImageJ software. Results: After single or combined laser treatment in mice aged 5 or 8 weeks, IOP was significantly elevated for 5 to 6 days before returning to the baseline by day 7 post-procedure. Anterior segment assessment indicated less synechiae in the anterior chamber angle and better preserved limbal vessels with single versus combined laser treatment. Corneal thickness was significantly increased after single or combined treatment. No inflammatory cells were detected in the anterior chamber. The thickness of the RNFL and the density of RGCs were both significantly reduced after single or combined treatment. Conclusions: Laser photocoagulation of episcleral veins alone in CD1 mice aged 5 to 8 weeks may be used to induce ocular hypertension resulting in RNFL thinning and ganglion cell loss. This model permits the study of the anterior as well as the posterior segment of the eye.

Reduced Scleral TIMP-2 Expression Is Associated With Myopia Development: TIMP-2 Supplementation Stabilizes Scleral Biomarkers of Myopia and Limits Myopia Development.

Purpose: The purpose of this study was to determine the endogenous regulation pattern of tissue inhibitor of metalloproteinase-2 (TIMP-2) in the tree shrew sclera during myopia development and investigate the capacity of exogenous TIMP-2 to inhibit matrix metalloproteinase-2 (MMP-2) in vitro and both scleral collagen degradation and myopia development in vivo. Methods: TIMP-2 expression in the sclera during myopia development was assessed using polymerase chain reaction. In vitro TIMP-2 inhibition of MMP-2 was investigated using a gelatinase activity plate assay and zymography. Tree shrews were injected with a collagen precursor before undergoing monocular form deprivation and concurrent daily subconjunctival injections of either TIMP-2 or vehicle to the form-deprived eye. In vivo ocular biometry changes were monitored, and scleral tissue was collected after 12 days and assayed for collagen degradation. Results: The development of myopia was associated with a mean reduction in TIMP-2 mRNA expression after 5 days of form deprivation (P < 0.01). Both activation and activity of MMP-2 were inhibited by TIMP-2 with an IC50 of 10 to 20 and 2 nM, respectively. In vivo exogenous addition of TIMP-2 significantly reduced myopia development (P < 0.01), due to reduced vitreous chamber elongation (P < 0.01). In vivo TIMP-2 treatment also significantly inhibited posterior scleral collagen degradation relative to vehicle-treated eyes (P < 0.01), with levels similar to those in control eyes. Conclusions: Myopia development in mammals is associated with reduced expression of TIMP-2, which contributes to increased degradative activity in the sclera. It follows that replenishment of this TIMP-2 significantly reduced the rate of both scleral collagen degradation and myopia development.

A Mouse Model of Chronic Ocular Hypertension Induced by Circumlimbal Suture.

Purpose: To develop a chronic ocular hypertension mouse model by inducing intraocular pressure (IOP) elevation using a suture technique previously developed for rats. Methods: C57BL/6 mice were given monocular circumlimbal suture (10/0) placement under anesthesia (ketamine/xylazine). The suture was left in place for 12 weeks (n = 10). A control group had the same treatment while it was removed after day 1 (n = 10). Intraocular pressure, electroretinogram (ERG), and optical coherence tomography (OCT) were measured in both groups for 12 weeks. At week 12, animals were euthanized and retina was harvested for histologic assessment. Results: In the group with extended suture placement, IOP spiked from 14.3 ± 0.9 to 48.4 ± 4.8 mm Hg immediately after suture implantation. At day 1, it declined to 33.2 ± 3.7 mm Hg and remained elevated for 12 weeks. In the suture removal group, IOP normalized to baseline within a day following suture removal. In the group with prolonged IOP elevation, the retinal ganglion cell (RGC) mediated ERG responses continued to exacerbate and were significantly reduced by week 12 (P < 0.001). Progressive loss of retinal nerve fiber layer was found and it became significant from week 4 (P < 0.001). At week 12, significant loss of RGCs (P < 0.001) was noted. In the IOP normalization group, no alteration in ERG, OCT, and RGC counting was observed. Conclusions: The circumlimbal suture approach produces a mild chronic IOP elevation in mice. Functional and structural changes under model induction are largely independent of the initial IOP spike.

Reversal of functional loss in a rat model of chronic intraocular pressure elevation.

PURPOSE: This pilot study considered whether intraocular pressure (IOP) lowering could reverse ganglion cell dysfunction in a rat model of chronic ocular hypertension. METHODS: A circumlimbal suture was applied in one eye to induce ocular hypertension (n = 7) in Long-Evans rats. The contralateral eye served as an untreated control. After 8 weeks of IOP elevation the suture was removed to lower IOP for the remaining 7 weeks. Electroretinogram (ERG) and optical coherence tomography (OCT) were measured at baseline, 2, 4, 8, 12 and 15 weeks. Retinae were collected for histology at week 15. RESULTS: In sutured eyes, IOP was elevated by 7-11 mmHg above control eyes (12 ± 0.2 mmHg [standard error of the mean]). Eight weeks of chronic IOP elevation resulted in a reduction of the ganglion cell mediated positive Scotopic Threshold Response (pSTR, -25 ± 7% of baseline), as well as smaller photoreceptor (-7 ± 4%) and bipolar cell mediated responses (-6 ± 5%). After suture removal, IOP recovered to normal. By 15 weeks the a-wave (0 ± 6%), b-wave (-2 ± 6%) and pSTR had recovered back to baseline (from -25 ± 7% to -4 ± 6%). The retinal nerve fiber layer was thinned by -9 ± 3% at week 8 and showed no further decline at week 15 (-10 ± 2%). Cell numbers in the ganglion cell layer were similar between suture removal and control eyes at week 15 (3543 ± 478 vs 4057 ± 476 cells mm-2 ). CONCLUSIONS: The circumlimbal suture model might be a useful platform to study the reversibility of neuronal dysfunction from chronic IOP challenge.

Chronic ocular hypertension induced by circumlimbal suture in rats.

PURPOSE: To induce chronic intraocular pressure (IOP) elevation in rat eyes by circumlimbal suture. METHODS: Anesthetized (isoflurane) Long-Evans rats underwent unilateral circumlimbal suture implantation while the fellow eyes served as untreated controls (n = 15). A sham group (n = 8) received the same procedure except that the suture was loosely tied. Intraocular pressure, electroretinography (ERG), and optical coherence tomography (OCT) were monitored for 15 weeks, after which retinal histology and immunofluorescence staining for glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule-1 (Iba-1) were undertaken. RESULTS: Both IOP and ERG remained unaltered in the sham and all control eyes over 15 weeks. In the ocular hypertensive eye, IOP spiked from 17 ± 1 to 58 ± 3 mm Hg immediately after suture application, recovering to 32 ± 2 mm Hg by 24 hours, and remained elevated by 7 to 10 mm Hg above baseline for 15 weeks. At week 2, there was a small reduction of ERG components involving the photoreceptor a-wave, bipolar cell b-wave, and ganglion cell-mediated scotopic threshold response (pSTR). The reduction in a- and b-wave remained stable, while the pSTR became more affected from week 8 onward (P < 0.05). By week 12, there was progressive retinal nerve fiber layer (RNFL) thinning. At week 15, GFAP expression was upregulated in inner retina and on Müller cells. The ganglion cell dysfunction was associated with RNFL thinning and cell loss in the ganglion cell layer. CONCLUSIONS: Circumlimbal suture provides a simple and cost-effective way to induce mild chronic ocular hypertension in rat eyes. This model produces preferential ganglion cell dysfunction and RNFL reduction.

Treatment of complex elbow injuries with a postoperative custom-made progressive stretching static elbow splint.

BACKGROUND: Complex elbow injuries consist of fractures of one or several of the bony stabilizers of the elbow, including the radial head, proximal ulna, coronoid process, collateral ligaments, and capsular complex. These injuries, if not properly treated, were reported to have a poor prognosis with recurrent instability, stiffness, posttraumatic arthrosis, and pain. This study was conducted to review clinical outcomes after fracture stabilization and ligament repair with a postoperative custom-made progressive stretching (CMPS) elbow splint in the treatment of complex elbow injuries. METHODS: From December 2001 to October 2006, 14 patients with complex elbow fractures or instability underwent surgery in Far Eastern Memorial Hospital by Chang Chih-Hung, using suture anchors. All patients used our CMPS static elbow splint postoperatively. No hinged elbow external skeletal fixator was necessary. The results were reviewed retrospectively. RESULTS: The patients were followed up for an average of 14 months. The mean (standard deviation) flexion-extension range of motion (ROM) was 116-degree angle (23-degree angle). The mean Mayo Elbow Performance Score was 92 points; the results were excellent in 10 patients, good in three patients, and fair in one patient. CONCLUSION: The dilemma in managing complex elbow injuries is that extended immobilization leads to stiffness, but without proper reconstruction of the stabilizer, joint instability recurs. Our surgical protocol included removal of all loose bodies within the joint, stable fixation of fracture fragments if possible, and use of suture anchors to repair medial or lateral ulnar collateral ligaments. CMPS static elbow splints provided both postoperative protection and ROM movement. In our experience, if the stabilizers were reconstructed, hinged elbow external skeletal fixator is usually not necessary, and progressive stretching by CMPS splint can result in good ROM.

Calcaneal osteotomy preoperative planning system with 3D full-sized computer-assisted technology.

In this study, we developed a CT-based computer-assisted pre-operative planning and simulating system for the calcaneal osteotomy by integrating different software's function. This system uses the full-scaled 3D reverse engineering technique in designing and developing preoperative planning modules for the calcaneal osteotomy surgery. The planning system presents a real-sized three-dimensional image of the calcaneus, and provides detailed interior measurements of the calcaneus from various cutting planes. This study applied computer-assisted technology to integrate different software's function to a surgical planning system. These functions include 3-D image model capturing, cutting, moving, rotating and measurement for relevant foot anatomy, and can be integrated as the user's function. Furthermore, the system is computer-based and computer-assisted technology. Surgeons can utilize it as part of preoperative planning to develop efficient operative procedures. This system also has a database that can be updated and extended and will provide the clinical cases to different users for experienced based learning.

Surgical treatment of acute acromioclavicular joint injuries using a modified Weaver-Dunn procedure and clavicular hook plate.

Various surgical procedures have been described for the treatment of complete acromioclavicular joint dislocation, but no consensus exists on the optimal therapy. The aim of each type of procedure is to stabilize the clavicle by substitution of the ruptured coracoclavicular ligaments. Treatment modalities have changed with increasing understanding of the nature of the problem and the biomechanics of the joint. This article presents a method consisting of a modified Weaver-Dunn procedure and a clavicular hook plate for the operative management of acute acromioclavicular joint injuries.We performed a retrospective study of 46 patients who had undergone a modified Weaver-Dunn procedure with a clavicular hook plate for acute acromioclavicular joint injuries between July 2002 and December 2006. Average follow-up was 36.6 months (range, 24-46 months). There was 1 skin-deep infection, 1 dislocation of the hook, and 2 redislocations of the acromioclavicular joint. Thirteen patients had some calcification between the clavicle and the coracoid process, which did not cause loss of motion or other symptoms. All but 1 patient returned to work, and all but 1 returned to their preoperative activity level. The mean Constant score was 88.2 points. The mean Disabilities of the Arm, Shoulder, and Hand (DASH) score was 12.2 points.Treatment of acute acromioclavicular joint injuries using a modified Weaver-Dunn procedure and a clavicular hook plate showed good short-term clinical results with a low complication rate. Further investigation and long-term results are needed to confirm these preliminary findings.

Comparison of plates versus intramedullary nails for fixation of displaced midshaft clavicular fractures.

BACKGROUND: We compare the use of plate and screws versus intramedullary nails in the operative management of patients with displaced midclavicular fractures. METHODS: Between March 2006 and June 2007, we performed a retrospective comparison of a demographically balanced sample of 110 patients (aged 16-65 years) who had received either plates or nails for completely displaced midshaft clavicular fractures. RESULTS: We selected 59 plate-fixed and 51 nail-fixed patients. There was no significant difference between the groups with respect to age, gender, height, dominant arm, fracture angulation, fracture shortening, total fracture displacement, or mechanism of injury. Outcomes were significantly higher in the plate group compared with the nail group for the length of hospital stay (4.6 days ± 2.1 days vs. 5.9 days ± 2.6 days, p = 0.006), operative blood loss (67.5 mL ± 36.2 mL vs. 127.9 mL ± 48.8 mL, p < 0.0001), and size of surgical wound (11.9 cm ± 4.4 cm vs. 22.3 cm ± 4.5 cm, p < 0.0001). There was no significant difference in operative time, time to union, restoration of mobility (forward flexion, abduction, external rotation, and internal rotation), number of nonunions, number of malunions, infection, need for hardware removal, early mechanical failure, time to return to work, and Constant Shoulder and Disabilities of the Arm, Shoulder, and Hand functional scores. CONCLUSION: Our results demonstrate no significant differences in functional outcome and nonunion rates between nails and plates fixation for displaced midshaft clavicular fractures.

Inhibition of matrix metalloproteinase activity in the chick sclera and its effect on myopia development.

PURPOSE: To investigate the contribution of matrix degradation in the two-layer avian sclera to the development of myopia. METHODS: Tissue inhibitor of metalloproteinase-2 (TIMP-2) was used to inhibit chick scleral collagen degradation with (3)H-proline, a marker for this effect. Ex vivo scleral culture experiments confirmed TIMP-2 doses for in vivo experimentation. Ocular growth and refractive response to exogenous TIMP-2 (11.25, 2.25, and 0.45 picomoles, plus vehicle only) were monitored in 7-day-old chicks during the induction of myopia over 4 days with a translucent occluder. Collagen degradation was assessed, in whole sclera and in separated scleral layers by using the same paradigm (11.25 picomoles TIMP-2; vehicle only). RESULTS: Approximately 60% of collagen degradation was inhibited with low (2 nM) doses of TIMP-2 in the ex vivo sclera. Degradative activity in the in vivo chick sclera increased significantly (46%) during myopia development, with all the altered activity confined to the fibrous layer. Addition of TIMP-2 significantly reduced (by 46%) this accelerated scleral collagen degradation, also by acting in the fibrous layer. TIMP-2 had no significant effect on (3)H-proline incorporated in the cartilaginous scleral layer and cornea. Despite inhibiting collagen degradation TIMP-2 had no significant effect on myopia development. CONCLUSIONS: Increased collagen degradation is a feature of scleral remodeling in chick myopia development, but is confined to the fibrous scleral layer. Significant inhibition of this collagenolytic activity with TIMP-2 has little effect on refractive error development, suggesting that collagen degradation in the sclera contributes little to the development of myopia in the chick.

Treatment of distal tibial metaphyseal fractures: Plating versus shortened intramedullary nailing.

BACKGROUND: Fractures in the distal tibial metaphysis are more complicated to treat than diaphyseal fractures. We compared treatment with plating to treatment with shorted intramedullary (IM) nailing. METHODS: Patients with AO type 43A fractures were treated with plate fixation (group A, n=14) or shortened IM nailing (group B, n = 13). We compared postoperative radiographic deformities, functional results (Iowa ankle scores), and symptoms (Olerud and Molander ankle scores). RESULTS: All fractures had healed at final follow-up (mean, 33 month). Mean union times were 27.8 week (range, 18-36 week) in group A and 22.6 week (range, 18-30 week) in group B (P<0.05). Mean postoperative valgus angulations were larger in group B (3.7 degrees ) than in group A (0.5 degrees ) (P<0.05). However, malunions did not differ between groups (P<0.05). Functional results and postoperative symptoms were similar. CONCLUSIONS: Both plate fixation and shortened IM nailing were effective for treating distal tibial metaphyseal fractures.